Characteristics of pyridine adsorption on Au(111) and Au(210) by EIS parameters fitting procedure

Some aspects of the application of electrochemical impedance spectroscopy to studies ofsolid electrode / solution interface, in the absence of faradaic processes, are analysed. In order to performthis analysis, gold electrodes with (111) and (210) crystallographic orientations in an aqueous solutioncontaining 10 mmol dm -3 KF, as supporting electrolyte, and a pyridine concentration varying from 0.01to 4.6 mmol dm -3 , were used. The experimental data was analysed by using EQUIVCRT software, whichutilises non-linear least squares routines, attributing to the solid electrode / solution interface behaviourdescribed by an equivalent circuit with a resistance in series with a constant phase element. The resultsof this fitting procedure were analysed by the dependence on the electrode potential on two parameters:the pre-exponential factor, Y 0 , and the exponent n f , related with the phase angle shift. By this analysis itwas possible to observe that the pyridine adsorption is strongly affected by the crystallographic orientationof the electrode surface and that the extent of deviation from ideal capacitive behaviour is mainly ofinterfacial origin.